In recent years, organic electroluminescent (EL) elements employing a thin organic film have come to be developed as thin film type electroluminescent elements in place of EL elements employing inorganic materials. An organic electroluminescent element usually has layers such as a hole injection layer, hole-transporting layer, luminescent layer, and electron-transporting layer between the anode and the cathode, and elements which emit light of a color, such as red, green, or blue, suitable for those layers are being developed. Since organic electroluminescent elements emit light by themselves, the elements attain a wide viewing angle and high visibility. The elements are attracting attention also from the standpoints of space saving, etc., because the elements are of the thin film type. In addition, organic electroluminescent elements have a feature that the elements emit light areally unlike the light-emitting diodes and cold-cathode tubes which have hitherto been in practical use. Owing to this feature, use of the elements in lighting devices, the backlights of full-color display devices in which color filters are used, etc. is also attracting attention.
Known as methods for forming the layers of an organic electroluminescent element are a vapor deposition method and a wet film formation method. However, the vapor deposition method has a problem concerning yield when TV receivers, monitors, medium- or large-size full-color panels for illumination, and the like are produced. The wet film formation method is hence suitable for these large-area applications (see patent documents 1 and 2).
For forming each of those layers of an organic electroluminescent element by a wet film formation method, it is desirable that the materials for constituting each layer should dissolve in a solvent and that the element obtained through the wet-process film formation should have high performance. From the standpoint of more efficient production, it is also desirable that the composition including the materials and the solvent should have high stability.
Meanwhile, it is known that pyrimidine derivatives and 1,3,5-triazine derivatives are suitable for use as a charge-transporting material, in particular, a material for organic electroluminescent elements, because these derivatives have high electron-accepting properties and a high electron mobility. For example, patent documents 3 to 6 and no-patent documents 1 and 2 disclose organic electroluminescent elements which employ those derivatives.